Vessel-loops, or vascular loops, are used by surgeons to occlude blood flow in blood vessels when performing a surgical anastomotic procedure (i.e., the surgical connection of two tubular structures, such as bypass surgery), and to hold or position an organ to facilitate or improve the visualization of a surgical site. Vessel-loops are used in different surgical procedures, including cardiovascular, thoracic vascular, orthopedic and urological surgery. A vessel-loop may include a hollow elastic tube having at least one end attached to a blunt pointed surgical needle. The elastic tube of the vessel-loop is hollow so that it flattens against the vessel when tension is applied, thereby providing a greater vessel surface-contacting area. The elastic tube is typically made of silicone rubber. The blunt pointed needle is used to guide the elastic tube through tissue. After the procedure is completed, the vessel-loops are removed from the patient.
Elastic silicone rubber tubes are also used in the manufacture of lacrimal stents, catheters and similar tubular devices used in dilating the lacrimal system. For example, these elastic tubes may be attached to a probe to introduce same into the nasal cavity of a patient (see, e.g., the devices disclosed in U.S. Pat. Nos. 5,169,386; 6,083,188; and 6,238,364).
Vessel-loops are typically manufactured using the following labor-intensive procedure. A length of hollow silicone rubber tubing is cut to form a silicone tube. A thin wire loop is used to manually pull the silicone tube into and through a section of hollow steel tubing which is later formed into a blunt pointed needle. A piece of catgut is then manually inserted into the silicone tube and manipulated therein so as to secure the silicone tube within the steel tube. The silicone tube is then pulled back so that one of its ends is positioned inside one end of the steel tube. This end of the steel tube is then closed using a Torrington machine, securing the end of the silicone tube thereto. The closed end is then manually ground and polished to form a blunt tip on the end of the steel tube distal to the silicone tube. The tip is then manually ground into a specified shape and polished. The resulting needle is then shaped so that a curve having a specified radius is formed. The silicone tube, which has been attached to the steel tube as it undergoes the foregoing processing steps to be formed into a needle, is then cut to a specified length. The silicone tube is then cleaned using alcohol, or another suitable solvent, and the needle is then siliconized. The resulting vessel-loop product may then be packaged, sterilized and distributed to end users (e.g., hospitals, etc.).
The manufacturing procedure described above presents several problems. One problem with this procedure is that the step of grinding the needle tip generates fusels and metallic debris, thereby making the procedure unsuitable for a “white area” abiding by good manufacturing practices (“GMPs”) in connection with the manufacture of medical devices. For instance, the attachment of the silicone tube to the steel tube at an early stage of the procedure results in the undesired handling of the silicone tube during the later steps of forming the needle. The silicone tube is therefore exposed to the fusels and metallic debris generated later in the process. The metallic debris is especially problematic in that it adheres to the silicone tube.
The procedure described above also includes several tedious manual steps in the assembly of the needle, making it inefficient and costly. The pulling, threading and securing of the silicone tube in the steel tube is especially difficult, exacting and complicated. Moreover, while the above procedure requires the use of catgut to secure the silicone tube within the steel tube, some countries have imposed bans on the use of catgut in surgical applications.
Another shortcoming associated with the above procedure is that the silicone tubes may only be used with needles which are manufactured using this procedure. In other words, needles made using other methods may not be compatible with the silicone tubes. The use of this procedure is thus limited.